1. Field of the Invention
This invention relates to an information-signal recording apparatus and an information-signal reproducing apparatus. Also, this invention relates to an information-signal recording and reproducing apparatus. In addition, this invention relates to an information-signal communication apparatus. Furthermore, this invention relates to an information-signal recording medium.
2. Description of the Related Art
A typical optical-disc recorder/player operates as follows. During a recording mode of operation of the recorder/player, a signal representing at least one of video information and audio information is compressed into a compression-resultant information signal. An optical head in the recorder/player records the compression-resultant information signal on an optical disc. During a playback mode of operation of the recorder/player, the optical head reproduces a recorded signal from an optical disc. The reproduced signal is expanded into an original information signal.
It is known to provide such an optical-disc recorder/player with a buffer memory having a capacity of about 4 Mbits. A recorded signal is reproduced from an optical disc at a transfer rate of 10.08 Mbps. The reproduced signal is converted into an information signal having a variable transfer rate lower than 10.08 Mbps. The buffer memory absorbs the difference in transfer rate between the before-conversion signal and the after-conversion signal.
Japanese published unexamined patent application 10-92158 discloses a disc reproducing apparatus designed as follows. Discontinuation and disturbance of an image are prevented by dividing a cell into a plurality of cells, time-division-multiplexing the cells in each scene and arranging and recording the cells to be reproduced continuously within the distance of the particular amount of codes to shorten the physical moving distance during the reproducing operation. In Japanese application 10-92158, a video program has a preceding front trunk scene A, a plurality of branch scenes B0 to B3, and a successive rear trunk scene C. In the case of recording a plurality of branch scenes on a recording medium, any branch scene is arranged in such a manner that a scene cell appears in the same rate for the summed total scene length. Arrangement should be done so that when the time for jumping the distance for the amount of particular codes is defined as Ts, the relationship Tc−[Tc×Pr/Rr]>Ts can be set for the amount of readout data Rr, amount of codes consumed Pr and image reproducing time Tc. When arrangement for recording is performed, a physical moving distance during the reproducing operation can be shortened and generation of discontinuation and disturbance of image can be prevented. The branch scenes B0 to B3 are multiple scenes. Each of the branch scenes B0 to B3 has a sequence of cells. The cells of the branch scenes B0 to B3 are shuffled before being recorded on a disc (a recording medium). Thus, the recorded cells of the branch scenes B0 to B3 are on non-successive separate positions on the disc. Accordingly, during the reproduction of the sequence of cells of one branch scene, a pickup head reproduces the cells and repetitively jumps between non-successive separate positions on the disc. In the apparatus of Japanese application 10-92158 includes a buffer memory capable of absorbing a time interval during which a pickup head jumps between non-successive separate positions on the disc so that reproduced data continue to be absent. Japanese application 10-92158 indicates the relation between the capacity of the buffer memory and a seek time of the pickup head which enables the buffer memory to continuously output data under conditions where the pickup head reproduces a sequence of cells of one branch scene and repetitively jumps between non-successive separate positions on the disc.
Japanese published unexamined patent application 6-139696 discloses a recording and reproducing apparatus which includes a buffer memory for absorbing a difference between transfer rates. In Japanese application 6-139696, during a recording mode of operation of the apparatus, first digital data having a lower transfer rate and being derived from an information signal to be recorded is converted into second digital data with a higher transfer rate. The second digital data are recorded on a disc at the higher transfer rate. During a playback mode of operation of the apparatus, third digital data are reproduced from the disc at the higher transfer rate, and the reproduced digital data are converted into fourth digital data related to the lower transfer rate. The fourth digital signal is converted into a reproduced information signal. The recording mode of operation and the playback mode of operation are implemented on a time sharing basis so that the information signal to be recorded and the reproduced information signal can simultaneously occur.